feature: add Mode function with tests and documentation

[ghosx]

add Mode function with tests and documentation

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.45%. Comparing base (49f24de) to head (c01b967).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #644      +/-   ##
==========================================
+ Coverage   94.41%   94.45%   +0.03%     
==========================================
  Files          18       18              
  Lines        3261     3281      +20     
==========================================
+ Hits         3079     3099      +20     
  Misses        170      170              
  Partials       12       12              

Flag	Coverage Δ
unittests	94.45% <100.00%> (+0.03%)	:arrow_up:

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